Fastener driving apparatus



Nov. 14, 1967 E. l. FISHER v FASTENER DRIVING APPARATUS '7 Sheets-Sheet l Filed Oct. 5, 1965 Nov. 14, 1967 E. FISHER FASTENER DRIVING APPARATUS Filed 001:. 5, 1965 Ff .5 2/5 Z/' 2/5190 j '7 Sheets-Sheet 3 E. l. FISHER Nov. 14, 1967 FAsTENER DRIVING APPARATUS 7 sheetssheet 4 Filed Oct. 5, 1965 E. I. FISHER FASTENER DRIVING APPARATUS Nov. 14, 1967 7 Sheets-Sheet 5 Filed Oct. 5, 1965 Nov. 14, 1967 E. FISHER FASTEN-ER DRIVING APPARATUS 7 Sheets-Sheet 6 Filed Oct. 5, 1965 United States Patent 3,352,471 FASTENER DRIVING APPARATUS Edward I. Fisher, Westerly, R.I., assignor to Bostitch Incorporated, East Greenwich, R.I., a corporation of Rhode Island Filed Oct. 5, 1965, Ser. No. 4%,110 23 Claims. (Cl. 227--7) ABSTRACT OF 'I'HE DISCLOSURE Fastener driving apparatus embodying a simple driving piston for moving a fastener driving element in a driving stroke through a drive track to drive a fastener received therein outwardly into a workpiece in which the driving piston is normally urged by source pressure acting on the driving element side of the piston into a position extending above the open end of the driving cylinder and into engagement with a piston stop to thus prevent communication of the pressure in a chargeable reservoir chamber therewith and in which the driving stroke is initiated as a result of exhausting the source pressure normally acting on the driving element side of the piston and subsequently accomplished through the action of the pressure in the chargeable reservoir chamber acting on the exposed opposite side of the piston. The return stroke of the piston is accomplished by restrictively exhausting the reservoir pressure acting on the opposite side of the piston while applying source pressure to the driving element side thereof. The reservoir chamber is recharged with source pressure at or near the end of the return stroke. The driving piston has a component formed of impact-absorbing urethane base material provided with a transverse passage and an intersecting blind hole, and the fastener driving element is held in the blind hole by a pin passing therethrough and engaged in the passage. The fastener driving apparatus also has a contact trip member movable from an inoperative position into an operative position by engagement with the workpiece to initiate the operation of the apparatus in conjunction with trigger actuation and a latch element movable into a first position locking the contact trip member in its inoperative position to render the apparatus inoperable, a second position locking the contact trip mem ber in its operative position rendering the apparatus trigger operable alone and a third position permitting workpiece engaged movement of the contact trip element and hence normal conjunctive operation of the apparatus.

This invention relates to fastener driving apparatus and, more particularly, to fluid actuated apparatus for driving fasteners.

It is an object of this invention to provide a powerful fastener driving apparatus of relatively light weight so that it is easy to handle for use as a portable implement.

Another object of the invention is to provide a pneumatically actuated fastener driving apparatus that incorporates simplified valving, is simple in construction, and facilitates routine maintenance.

Still another object of the invention is to provide novel and improved compact fastener driving apparatus of the pneumatically actuated type which has a relatively low recoil so that it is relatively easy to use as a portable instrument without damage to the surface in which the fastener is driven.

Another object of the invention is to provide a novel and improved pneumatically actuated fastener driving implement in which the length of the driving stroke is increased relative to the total height of the implement.

Another object of the invention is to provide a simple and reliable interlock valve latch structure.

A further object of the invention is to provide a novel and improved pneumatic engine control arrangement which prevents unintended firing of the engine in response to initial application of fluid pressure thereto.

Still another object of the invention is to provide a novel and improved fastener driving apparatus which facilitates the interchange of different sizes and type of fasteners and magazines.

Fastener driving apparatus constructed in accordance with the invention includes a cylinder housing a piston having secured to one side thereof a fastener driver. Disposed above the open end of the cylinder but spaced therefrom is a piston stop-valve structure which includes a seal portion for engaging the piston surface opposite the driver element to provide an annular seal. The apparatus also includesa reservoir chamber for supplying pressure fluid to the cylinder through the open end thereof and the piston in its raised position blocks the port between the reservoir and the cylinder. Control means are provided for creating a pressure differential across the piston to move the piston away from the piston stop in a driving stroke and that movement opens the port between the reservoir and the cylinder to expose the piston to full fluid pressure.

In a preferred embodiment, the piston stop is a movable element which performs a valving function to block communication between the supply line and the reservoir during the driving stroke. There is also employed in that embodiment a combined fastener driver and piston stop bumper made of an impact-absorbing material such as urethane and of a configuration that facilitates the flow of air from the cylinder during the driving stroke of the piston. The piston itself is preferably of lightweight material and may be of the same material as the bumper.

In the disclosed embodiments, the fluid pressure differential is created across the piston through use of a large rapidly acting dump valve which opens the entire portion of the cylinder below the piston to atmosphere and releases the piston for the downward power stroke. Full fluid pressure is applied as soon as the annular seal at the top surface of the piston is broken. The construction of the preferred embodiment also includes a workpiece interlock and a latch structure for controlling the operability of that workpiece latch-interlock from the housing and the re moving of a base plate so that the bumper stop, piston and driver element may be removed and replaced by the appropriately modified driver element with corresponding magazine and bumper stop.

Other features, objects and advantages of the invention will be seen as the following description of particular embodiments thereof progresses in conjunction with the drawings, in which:

FIGURE 1 is a side elevation-a1 view, in section, of a preferred form of fastener driver apparatus constructed in accordance with the invention;

FIGURE 1A is a front view of the lower portion of the fastener driving apparatus shown in FIGURE 1 showing details of the workpiece latch-interlock;

FIGURE 2 is a top plan view of the fastener driving apparatus shown in FIGURE 1 with parts thereof broken away;

FIGURES 3-7 are sectional views of the apparatus taken along the lines 33, 4-4, 5-5, 6-6, 7-7 of FIGURE 1, respectively;

FIGURE 8 is a sectional view taken along the line 8-8 of FIGURE 5 showing details of the trigger, interlock, and exhaust valves;

FIGURE 9 is a sectional view similar to FIGURE 8 showing the valve elements in :a second position;

FIGURE 10 is a perspective view of the insert for the dump valve;

FIGURE 11 is a perspective view of a bushing component of the trigger valve assembly;

FIGURE 12 is a sectional view similar toFIGURE 1 showing the components of the apparatus in a second driving position;

FIGURES 13-15 are views of three modified piston configurations suitable for use in the apparatus shown in FIGURES 1-12;

FIGURE 16 is a sectional view of a second embodiment of fastener driving apparatus constructed in accordance with the invention;

FIGURE 17 is a view of the apparatus shown in FIG- URE 16 in a second position;

FIGURE 18 is a sectional view of still another embodiment of apparatus constructed in accordance with the invention;

FIGURE 19 is a sectional view taken along the line 1919 of FIGURE 18;

FIGURE 20 is a sectional view of the apparatus shown in FIGURE 19 showing components thereof in a second position; and

FIGURE 21 is a sectional view taken along the lin 21-21 of FIGURE 20. r

The apparatus shown in FIGURE 1 is a pneumatically operated fastener driver capable of driving fasteners such as nails in a single stroke. The illustrated apparatus includes a housing having a head portion 12 and a handle portion 14 that extends rearwardly from the head portion. Disposed in the head portion 12 is the driving cylinder 16 that houses a driving piston 18. Connected to the piston 18 in suitable manner as by pin 21) is a fastener driving blade 22 which extends downwardly from the piston through a passage in the base plate 24 secured to the bottom of housing 10 into a nail drive track at the forward end of magazine structure 30. That magazine structure may be of conventional design arranged to hold a supply of fasteners. As indicated, it is secured to the forward end of the housing by a bracket 32 and bolts 34, and to the rearward end of the housing by studs 36.

At the upper end of cylinder 16 is a cylindrical port 40 which provides communication between the cylinder and a reservoir chamber 42 in the handle portion. In the top wall of the head portion above the end of cylinder 16 and coaxial therewith is a second port 50 of larger diameter than cylinder 16 which provides communication to a chamber 52 defined in closure cap structure 54 that is secured on the housing 10 by means of suitable fasteners such as bolts 56 (FIGURE 2). Chamber 52 thus cornmunicates through port 50 with reservoir 42.

Depending from the upper wall of the cap 54 is a cylindrical boss 60 having an internal cylindrical surface 62 that receives a piston stop and valve structure 64. That structure has a flange portion 66 at its base and an upstanding cylindrical portion 68. The flange portion has disposed over it a boot 70 of resilient material that provides an upper surface 72 which acts as a stop against the lower edge of the cylindrical boss 60 and a lower surface 74 which performs two valving functions, a first valving function in cooperation with piston 18 and a second valving function relative to port 50. Extending inwardly from the cylindrical portion of structure 64 is a second flange 76 on which is seated a compression spring 78 which acts between flange 76 and an opposed inner surface of cap 54 to urge the stop-valve structure 64 downwardly. A groove 80 in the interior wall of boss 60 receives an O-ring 82 which functions to provide a seal between a stop-valve structure and the boss.

At the lower end of the cylinder 16, there is a main exhaust port or channel 90 through the cylinder wall which extends into a dump valve chamber. An insert 92 (shown in FIGURE 10) is disposed in the dump valve chamber and has a transverse port 94 in alignment with the cylinder channel 90 and axial port 96 in alignment with a corresponding dump port 98 in the housing end plate 24.

The bore in which this insert is disposed extends upwardly and forms a cylinder chamber 110 in which an actuating piston 112 for dump valve element 114 moves. The dump valve 114 is of smaller diameter than the piston 112 and is secured to that piston by stem 116.

The housing further includes a transverse passage that communicates through port 122 with the upper end of chamber 110. This transverse passage 120 also communicates with a second passage 124 which connects it to the trigger valve chamber 130. The trigger valve structure includes a ball 132 which is movable between an exhaust port 134 in a bushing 136 and an opposed supply. port 138. Supply port 138 is directly connected to supply chamber 140 which is connected via conduit 142 to a suitable source of fluid pressure. A detachable coupling (not shown) typically may be provided at the end of the conduit 142. The supply chamber 140 also is in direct communicntion (through port 100) with the lower surface of the dump valve piston 112.

The trigger valve structure, as shown in FIGURES 1, 5 and 7 is disposed in chamber 130 in the handle portion 14 of the housing. Depending below and extending laterally on either side of the chamber 130 are two parallel wall portions 152, 154. Pivotally secured between these wall portions 152, 154 is a trigger member 156 which has a notched surface 158 arranged to engage a push rod 160 of cruciform configuration (see FIGURE 5). This push rod is disposed in the exhaust port bore 134 of bushing 136. As indicated in FIGURE 11, the bushing includes opposed lateral projections 162, 164 and these are received in slots 166 in the walls 152, 154. In securing this bush ing to the valve chamber 130, it is initially positioned with the projections 162, 164 parallel to the walls 152, 154 and then rotated 90 so that the projections enter and are secured in slots 166. The trigger member is then pinned in place so that its vertical surface 168 secures the bushing against rotation so thatit remains secured in slots 166 closing the valve chamber. 7

Further valving included in the tool is best indicated in FIGURE 8. That valving includes an exhaust valve structure and a safety interlock valve structure. An exhaust channel in cap 54 extends from a port in the interior of the cylindrical boss (above groove 80) through horizontal passage 170 and vertical passage 172 in the cap into an exhaust valve chamber 174 formed at the junction between cap 54 and housing body 10. A valve seat 176 formed in that chamber on housing 10 is disposed above a lateral exhaust passage 178 (which is indicated in rotated position in FIGURE 8). The valve element 180 which cooperates with and engages seat 176 is operated by a piston 182 which is disposed in cylinder 184 below valve chamber 174. The lower end of the cylinder is connected to passageway 186 which intersects passage 120. Thus, when the dump valve piston 112 is subjected to downwardly directed pressure, the exhaust valve piston 182 is subjected to upwardly directed pressure.

The interlock valve structure includes a rod 190 disposed in a bore, the extension of which forms passage 192 which connects the chamber 52 in the cap with the supply chamber 140. Rod 190 has a first valving section 193 at the top of the rod and a second valving section 194 of reduced diameter below section 193. The lower end 196 of the rod engages a contact trip actuating structure 198 that is secured to the nose piece of the magazine.

Details of this structure are best seen in FIGURES 1 and 1A. The contact trip includes a body 200 disposed for vertical sliding movement on the nose piece structure 202. Depending from the body is a contact trip element 204 that normally projects below the nose piece as shown in 212 which may 'be positioned in any one of the three indicated positions to control the operability of the contact trip. In the solid line position, the latch 212 engages the lower horizontal surface of slot 208 and latches the contact trip in its fully down position (preventing operation of interlock valve 199); in the vertical dotted line position latch 212 engages the upper horizontal surface of slots 208 so that the contact trip is latched in its fully up or actuated position; while in the horizontal dotted line position, the latch surface of link 212 is spaced from both slot surfaces and the contact trip is free to respond to engagement with a workpiece. The latter is the position of the latch 212 during normal operation of the tool.

When latch 212 is in the third (normal) position and the nose piece is in contact with a workpiece W (as indicated in FIGURE 12), contact trip structure 198 raises rod 190 so that its valving section 194 is aligned with passages 124 and 186 and its upper end closes the direct connection between supply chamber 140 and passageway 120. Thus, when this interlock valve element is in its normal position, the trigger valve is bypassed so that the exhaust valve and the dump valve are directly exposed to fluid pressure from the supply chamber. When the interlock valve element 199 is raised, it closes the direct passage and places those valves under the control of the trigger valve structure.

A further structural feature of the implement is the configuration of piston bumper 214 secured in the base of the main cylinder 16. This bumper is preefrably constructed of an impact-absorbing material such as urethane and includes a central slotted opening aligned with a corresponding slot in plate 24 through which the driver 22 slides. This bumper has raised lands 216, which provide a substantial surface area for stopping the piston and absorbing the impact of that piston in its downward stroke. Disposed between these lands are upstanding relatively flexible lip portions 218 which surround the driver blade 22 and provide a seal of the driver blade at that point to prevent the escape of fluid along the driver blade. Extending radially outwardly and downwardly from land 216 is an arcuate channel 219 which provides a passage of ample dimensions to the exhaust channel 90. In the preferred embodiment, the bumper seal is of symmetrical configuration with a second arcuate channel so that assembly of the bumper, the driver and the piston into the piston 16 is facilitated. If desired, portions of the lands may be slightly recessed (as indicated by dotted lines in FIGURE 6) to allow release of air that might otherwise be trapped under the piston in the area of the lips 218.

In operation, spring 73 initially urges stop-valve structure down so that port 50 between cap chamber 52 and reservoir chamber 42 is closed. When air under pressure is applied through conduit 142 to supply chamber 140 with the trigger and interlock valve elements in the position shown in FIGURE 1, that pressure, as applied through passage 124, acts on the upper surface of the dump valve piston 112 and forces it downwardly closing the dump port 98. Also, the air flows upwardly through passage 186 to open the exhaust valve so that air pressure in the chamber above the .piston is exhausted through the passages 170, 172, 178. Further, the air in supply chamber 140 is applied through the insert 92 to the main cylinder channel 90 to act on the under side of piston 18 and force it upwardly to the position shown in FIGURE 1. In that position, the piston protrudes out of the end of the cylinder having opened port 56 after the upper surface of the piston is sealed against resilient sealing surface '74. (The initial closure of port 59 provides a safeguard against unintended driving of the piston due to connection of the tool to the air supply and it will be noted that a further safeguard is provided by the use of supply chamber 149 and interlock valve 196 disposed in the passage between the supply chamber and the reservoir 42.) In this position, a seal between the reservoir 42 and the cylinder 16 is provided by the piston itself with the central upper surface of the piston exposed to atmospheric pressure while the opposite surface of the piston is exposed to supply pressure, holding the piston in its raised or retracted position. Reservoir 42 is rapidly charged through the large annular port 50 surrounding the cylindrical surface of the piston 18 that projects above the open end of the cylinder 16.

When the nose piece of the tool is placed in contact with the workpiece W as shown in FIGURE 12, the interlock valve element 190 is raised placing the section 194 of reduced diameter in alignment with the passageway 124 and closing off direct connection from supply chamber 140 to passages and 192. However, passageways 120 and 186 remain pressurized as a connection to supply chamber remains through port 138 as controlled by trigger valve 132. When the trigger 156 is pressed, the push rod 160 is raised and lifts the ball 132 up to close port 138 and exhaust passages 120, 124 and 186 to atmosphere through exhaust port bore 134. Also, pressure in the dump valve cylinder 11%] above piston 112 and in the exhaust valve cylinder 184 below piston 182 is reduced.

As supply pressure is directed against the lower side of the dump valve piston 112, that piston is moved upwardly under the influence of the pressure differential across it. The cylindrical valve structure is of a length so that as it moves upwardly, it closes the intermediate axial port 99 in insert 92 before the lower port 96 is opened. Also, the valve rapidly moves to fully open position as the valve 114 is of smaller diameter than the piston 112 so that a pressure differential continues to exist after port 53 is closed. The dump valve moves rapidly to its upper position as shown in FIGURE 12 opening the dump port 98 so that the air in the cylinder 16 beneath the piston 18 is dumped to atmosphere. This allows the piston 18 to move downwardly, initially under the influence of spring 78. As soon as the pistons upper surface breaks away from the seal surface 74, reservoir pressure is exerted on the entire upper surface of the piston and forces that piston rapidly downward in a powerful driving stroke to drive the fastener disposed in the drive track into the workpiece W. As soon as the piston has moved away from the piston seal surface 74, pressure is also applied through the exhaust passageway and acts on the upper end of exhaust valve piston 182 to drive that piston downwardly and move the valve element into engagement with the valve seat 176 to close the exhaust passage 178 and thus conserve air.

It will be noted that the piston stop moves downwardly against the seat in the top of the housing and closes port 56 between reservoir 42 and chamber 52. The pressure for driving the piston is thus directly and solely derived from reservoir 42. As the volume of reservoir 42 is several times the volume of the cylinder 16, there is no significant impairment of the available driving force.

As soon as the tool is raised from the workpiece, releasing the interlock valve 190, or the trigger valve 132 is released, pressure is again supplied to passage 126 to act against the top surface of piston 112, first to close the dump valve ports 96, 98, and then to allow fluid from supply chamber 140 to flow through lower cylinder channel 9t] and act against the lower surface of driving piston 18 to raise it. Also, the pressure from supply chamber 146 opens the exhaust valve 180 thereby lowering pressure in chamber 62 and insuring consistent piston return. As the piston reaches the upper end of cylinder 16, it seats firmly on the stop-valve structure and then raises that structure to open port 50 and permit reservoir 42 to be brought up to line pressure.

The structure may be modified in numerous respects without departing from the invention. For example, the plastic piston shown in FIGURE 1 preferably is made of an impact-absorbing material such as urethane. The piston includes an axial aperture in which driver 22 is received, a transverse bore intersecting the axial aperture and a circumferential groove intersecting the transverse bore.

A metal pin is received in the bore in press fit relation and extends through an aperture in the driver 22. The metal pin in turn is positively secured in position by an O-ring positioned in the circumferential groove. Other types of piston configurations that may be utilized in the driving implement are shown in FIGURES 13-15. The piston 420 shown in FIGURE 13 is substantially the same type of piston with driver 22' being secured with metal pin 20 and a locking O-ring disposed in the circumferential groove. Below the circumferential groove, there is a protrusion 422 which is formed integrally with the plastic material of the piston and functions as the sealing member for engagement with the wall of the cylinder. A similar construction is shown in FIGURE 14 having the same components except that the piston seal is provided by a protrusion 424 having circumferential slots 426 and 428 on either side of the protruding seal portion 424 to increase the resiliency and flexibility of that seal portion. A fourth form of lightweight piston is indicated in FIGURE 15. That piston includes a shell 430 of aluminum or other suitable material that has a circumferential groove 432 in which an O-ring 434 is disposed. The shell is supported by an insert 436 of plastic such as urethane which includes a recess having entrance walls 438 and a base portion 44$ of larger dimension than the space between walls 438. A driving element 22" is inserted in the recess between the walls 438 so that an enlarged portion 442 of that driver is seated in base portion .440. The plastic insert with the driver member secured to it is then inserted in the shell 430 and secured therein by suitable means either by a press fit, adhesive or mechanical fasteners. In each of these arrangements, it will be noted thatthe piston is a compact structure of low mass and depth so that the height of the tool necessary for a full driving stroke is reduced. The recoil of the tool during a driving stroke is also reduced. Further, in each of these piston structures, the upper peripheral surface is smooth and no sealing memberneed be disposed on that end surface or on the cylindrical surface portion that protrudes out of the upper end of the cylinder when the top surface of the piston is sealed against the piston stop. It will be noted that in the embodiment illustrated in FIGURE 1, for example, it is not necessary for a fluid barrier to exist in between its base and the cylindrical wall. However, the top surface of the piston (that inside of the annular seal) must be sealed from the cylindrical surface as well as from the bottom of the piston for maximum eiiiciency.

In these constructions, it will be noted that it is extremely simple to change the size of the driver and fasteners to be driven. All that need bedone is to detach the magazine by releasing the bolts 34 and 36 and remove the housing base plate'24, bumper 214, and piston 18 with driver 22. A new driver'of' suitable configuration to conform 'to the fastener to'be driven is then secured to the piston or another piston with suitable driver already attached is reinserted in the cylinder, a bumper positioned in the base of cylinder 16, and a substitute base plate having an aperture of appropriate dimension corresponding to the configuration of the'driver is secured to the housing. The appropriate magazine is then connected to the housing by means of bolts 34 and 36 and the implement is ready for use.

A second embodiment of fastener driving apparatu is shown in FIGURES 16 and 17. That apparatus includes a housing 229 having a handle portion 222 which extends rearwardly and a body portion 224 which defines piston cylinder 226 extending downwardly from the for- 'ward end of thehandle..Disposed in the cylinder for reciprocating movement is a piston 22% that has a body portion 230 and an upstanding cylindrical portion 232. Secured to the body portion of the piston is a driver element 234 that extends downwardly through the piston cylinder and base plate 236 into the'drive track of the 8 magazine structure 238 adapted for use with the driving engine.

A piston stop-seal structure is fixedly mounted above the open upper end of cylinder 226. This stopseal structure includes an annular surface 240 to which is secured a sealing element 242. Located inwardly of the sealing member 242 and depending therefrom is a fixed piston guide structure 244 which is received within the cylindrical portion 232 when the piston is in its upper (sealing) position. Also,.located in the stop structure is an exhaust conduit including orifice246 and passage 248 which extends through the cap 255} to the atmosphere.

In the bottom of the piston cylinder 225 is a bumper I 252 which is supported on valve housing 254. Disposed in housing 254 is a plurality of exhaust passages 256,. A flexible diaphragm type of valve member 258 has an outer peripheral portion 260 secured between the valve housing 254 and the base plate 236. The inner peripheral portion includes an upturned lip portion 262 and engages the driver element 234. A driver seal 264 is'positioned V in groove 266 in base plate 236.

'Also disposed in valve housing 254 is a supply port 270 connected to supply line 272 and a valve chamber 274. The valve chamber includes an inlet port 276 in communication with supply port 2749, an outlet port 278 in communication with the lower surface of flexible diaphragm 258, and an exhaust port 289. A valve member 282 which is coupled by link 284 to trigger 236 includes the valve elements 288, 29%). The valve member is normally in raised position as indicated in FIGURE 16'so that valve element 299 closes exhaust port 230 and the inlet port 276 is opened so that air from the supply line 272 is applied to raise the diaphragm 258 and seal the exhaust passage 256. At the same time, the pressure against the lower side of the unsupported lip 262 flexes that lip so that air flows upwardly along the driver element 234 and acts against the lower side of piston 228 to raise it and maintain it against the piston stop valve structure 246. There is also provided in the Wall of the cylinder 226 immediately below the lower surface of the piston body 228 when it is in the raised position, a port 292 with a flapper valve structure 294. This 'port provides communication between the lower portion of the cylinder 226, and the reservoir 296 in the handle 222. The flapper valve 294 is mounted in conventional manner so that it closes when the pressure in the cylinder is less than the pressure in the rservoir 296, thus conserving reservoir pressure at initial actuation of the tool.

Operation of the implement is in response to downward movement of control valve 282 actuated by the trigger 286 to close inlet entrance port 276 and open exhaust port 280. When this occurs, the pressure on the lower side of diaphragm 258 is exhausted to atmosphere and the diaphragm fiexes downwardly to open the main exhaust passages 256 'so that-the entire volumeof cylinder 226 under piston 228 is exhausted rapidly. Air pressure acting on the piston seal.

moves the piston away from the main seal 242 so that the entire top of the piston is exposed to reservoir pressure for driving rapidly downward.

When the control valve 282 is released to close exhaust port 280, the supply pressure is readmitted to the underside of diaphragm 258 and forces that diaphragm up to close the dump passages 256. This air pressure also flows upwardly past the lip 262 on the diaphragm into the piston cylinder 226 and forces the piston up. As the piston returns to seat against annular seal 242, the valve 294 remains closed until the lower edge of the piston clears passageway 292, at which time that flapper valve opens for recharging the reservoir. It will be noted that the depending guide 244 for the piston traps air which is slowly exhausted through orifice 246 and, hence, acts as a buffer to slow the piston down so that it seats smoothly on the resilient seal 242 with a portion of'the piston protruding out of the open end of cylinder 226.

Still another embodiment of the invention is shown in FIGURES 1821. That device includes a housing 300 which includes a rearwardly extending handle portion 302 having a reservoir chamber 304 therein, and a head portion having a cylinder 308 therein. The upper end 310 of cylinder 308 is open and secured above it to seal the upper end of the housing is a cover plate 312 from which depends a fixed piston stop and seal structure 314. An exhaust passageway 316 extends from outlet port 318 to a restricted orifice 320 in the base of stop structure 314. At the bottom of the cylinder 308 is secured a valve assembly structure 330 which provides a lower cylinder seal. A bumper of impact-absorbing material 332 and a cylindrical guide structure 334 are supported on and above the valve structure. Disposed in cylinder 308 is a piston 340, the upper surface of which, when the piston is in retracted position, engages a resilient member 342 carried by the piston stop structure so that an annular seal is provided at the pistons upper surface. The cylindrical wall of the piston includes a recess 344 in which is disposed a sealing member 346. The piston 340 is of a light metal such as aluminum with portions removed to reduce its mass. Secured to the piston in suitable manner is a driver element 350 which extends through the base (valve assembly) block 330 for movement through a driver track which is in communication with the magazine (not shown).

When the piston is in its up position as shown iri FIG- URE 18, a passageway 360 in upper wall of the piston is uncovered and provides a path for fluid flow between the piston cylinder 308 and the reservoir chamber 304.

Also disposed in housing 300 is a vertical bore 368 which extends parallel to the piston cylinder 308 and has disposed in it a valve assembly 370 including an upper valve element 372, intermediate valve element 374, and two lower valve elements 376, 378, all integral with common connecting rod 379. These valve elements are actuated in response to movement of trigger 380 via coupling link 382. The upper valve element 372 controls the flow of fluid through passage 360 to the reservoir 304; valve element 374 serves an isolating function; valve element 376 cooperates with seat 384; and valve element 378 cooperates with seat 386 at exhaust port 388.

The main valve assembly 330 includes a cylindrical main valve chamber 390 which houses a dump valve 392. That valve is secured to piston 394 by valve stem 396. Piston 394 slides in cylinder 398 which is of larger diameter than valve chamber 390. An intermediate chamber 399 communicates with supply line 400 via passage 402. Also, communicating with the chamber 399 is control passage 404 which enters valve bore 368 below the intermediate (isolating) valve element 374. A fourth port in bore 368 communicates with passage 406 which passes through a groove in cover plate 408 and enters the end of the cylinder 398 and controls the piston 394 reciprocally housed in that cylinder.

The valving block 330 also includes a large exhaust port 410 at the end of the chamber 390 and a passage 412 into the center base of the piston cylinder 308. When the dump valve 392 is in the position shown in FIGURE 19, its O-ring 414 seals the exhaust port 410. In this position, air pressure through line 400 passes through the chamber 399, around the valve stem 396 and into passageway 412 to act directly against the bottom of piston 340 to hold it in its upper position against the valve seat 342. The pressure fluid also passes through passage 404 and downwardly past valve element 376 for return through passage 406 to act on the surface of piston 394 and hold the dump valve in position shown in FIGURE 19. At this time, fluid pressure from cylinder 308 passes through passage 360 to charge reservoir 304 to full line pressure.

When the trigger 380 is depressed, the control valve assembly is lifted, moving the upper valve element 372 above passage 360 to terminate reservoir charging, the lower valve element 378 to open the exhaust port 388,

and valve element 376 to close the link between passages 404 and 406. This operation effectively dumps the air in the cylinder 398 to atmosphere so that the pressure in chamber 390 acting on the opposite side of piston 394 moves the dump valve 392 rapidly to the position shown in FIGURE 21 opening dump port 410 so that the bottom of the main cylinder 308 is exposed to atmospheric pressure. The pressure in the reservoir, however, remains acting on the small exposed portion of the upper surface of piston 340 (note that valve 372 has closed passage 360). With the reduction of pressure on the lower surface of the piston 340, that piston moves downwardly and, as its upper surface breaks free from the seal 342, its entire upper surface is exposed to pressure from the reservoir and the piston and driving element 350 are forced downward rapidly in a power-driving stroke.

The implement resets upon release of trigger 380 which returns the control valve structure 378 to the position shown in FIGURE 18. In this position, exhaust port 388 is closed and the link between passages 404 and 406 is opened so that pressure acts on the dump valve piston 394 to close the dump port 410. As soon as the dump port is closed, line pressure is impressed on the bottom of piston 340 and it is driven upwardly in the resetting operation. A substantial portion of the fluid in cylinder 308 is returned to reservoir 304 during the return stroke. The dimensions of exhaust orifice 320 are selected so that an optimum balance is obtained between cycle speed and loss of fluid during cycling. The exhaust orifice 320 permits the piston 340 to seat firmly against the seal 342 without bouncing. As soon as the lower edge of the piston skirt has moved past port 360, the pressure in the cylinder chamber also flows into the reservoir 304 to recharge that reservoir as necessary in preparation for the next driving stroke of the implement.

While particular embodiments of the invention have been shown and described, further modifications will be obvious to those skilled in the art and, therefore, it is not intended that the invention be limited to the disclosed embodiments or to details thereof and departures may be made therefrom within the spirit and scope of the invention as defined in the claims.

What is claimed is:

1. A pneumatic driving tool comprising a cylinder having an open end, a piston disposed in said cylinder for axial movement between first and second positions including a driving stroke in a direction away from the open end of said cylinder, a fastener driving element secured to said piston at one end thereof, a piston stop spaced above said open end of said cylinder including a first surface portion for engaging the piston surface opposed to said one end to provide an annular seal between said piston stop and said piston when said piston is disposed in said first position, means defining an exhaust passage having an orifice disposed for communication with said opposed surface of said piston inside the area of said annular seal, a reservoir chamber for supplying fluid pressure to said cylinder through the open upper end thereof in a piston driving stroke, a first port adjacent said open end of said cylinder, said piston when in said first position having a surface portion protruding beyond said open end of said cylinder for blocking communication between said reservoir chamber and said cylinder through said first port, said first port being fully open during the driving stroke of the piston away from said piston stop, and control means maintaining a normal pressure differential across said piston when the latter is disposed in said first position urging said piston into said first position operable to change said normal pressure differential into one resulting in movement of said piston away from said piston stop whereby said piston is moved through a driving stroke under the action of the pressure in said reservoir chamber.

2. The tool as claimed in claim 1 wherein said control means includes valve means movable between a first posi- 1 1 tion connecting said cylinder at the end thereof opposite said open end with a source of fluid pressure for urging said piston toward said piston stop and a second position connecting said opposite cylinder end to atmosphere for venting said cylinder.

3. The tool as claimed in claim 2 wherein said valve means includes a valve element and an operating piston coupled thereto, the effective dimension of said operating piston being greater than the corresponding dimension of said valve element.

4. The tool as claimed in claim 2 wherein said valve means includes a flexible diaphragm member.

5. The tool as claimed in claim 1 including a control chamber adjacent said reservoir chamber and a second port communicating said control chamber with said reservoir chamber, and wherein said piston stop includes a second surface portion for sealing said second port, said piston stop being mounted for movement between a second port sealing position and a second port opening position, and further including spring means for urging said piston stop towards said second port sealing position.

6. The tool as claimed in claim 5 wherein said second surface portion is an annular portion disposed outwardly of said first surface portion.

7. The tool as claimed in claim 5 wherein said piston when urged into engagement with said piston stop moves said second surface portion away from said sealing position into said opening position. a

8. The tool as claimed in claim 1 and further including an exhaust valve for controlling the flow of fluid through said exhaust passage and manually operative means for operating said exhaust valve and said control means.

9. The tool as claimed in claim 1 wherein said exhaust passage defining means is integral with said piston stop.

10. A pneumatic fastener driving implement comprising a housing, a cylinder disposed in said housing having an upper end and a lower end, a nosepiece structure defining a drive track for receiving fasteners from a magazine, means securing said nosepiece structure to said housing adjacent the lower end of said cylinder, a piston disposed in said cylinder for axial movement away from said upper end in a driving stroke, a fastener driving element secured to said piston at one end thereof for movement through said drive track during a driving stroke of said piston, said piston having a component of polymeric impact-absorbing material, said piston further including a transverse passage extending therethrough and a blind hole extending into said piston from said one end and intersecting said transverse passage, said fastener driving element being disposed in said blind hole, a pin disposed in said transverse passage for securing said driving element to said piston, and an annular resilient element extending around said piston at a point intermediate said transverse passage and said one end for providing sealing engagement with the inner surface of said cylinder.

11. The implement as claimed in claim wherein said impact-absorbing material includes a urethane base material.

12. The implement as claimed in claim 10 wherein the body of said piston consists of said polymeric impactabsorbing material and said annular resilient element is formed integrally with said body and projects outwardly beyond the main annular surface portion of said body.

13. The implement as claimed in claim 12 and further including an annular recess on either side of said annular resilient element for increasing the ability of that element to flex relative to the rest of the piston.

14. Fastener driving apparatus comprising housing means defining a drive track for receiving therein fasteners to be driven, power operated fastener driving means carried by said housing means and including a fastener driving element movable through said drive track in a fastener driving stroke to drive a fastener received in said drive track outwardly thereof into a workpiece in response to the actuation of said power operated fastener driving means, manually operable means mounted on said housing means for manual movement from an inopera tive position into an operative position, a contact trip member mounted on said housing means for movement by engagement with the workpiece from an inoperative position, and a third position permitting movement of said power operated fastener driving means in response to the movement of said manually operable means and said contact trip member into said operative positions respectively, and latch means mounted on said housing means for movement into a first position locking said contact trip member in said inoperative position, a second position locking said contact trip member in said operative position, and a third position permittiing movement of said contact trip member between said operative and inoperative positions.

15. Apparatus as defined in claim 14 wherein said latch means is an elongated member having a latch surface at one end, and said contact trip member includes two. op-

posed surfaces, and further including means for mount ing said latch member on said housing means between said opposed surfaces for pivoting movement about the fastener driving element secured to said piston at one end thereof for movement through said drive'track during a driving stroke of said piston, a piston stop spaced above said open end of said cylinder including a first surface portion for engaging the piston surface opposed to said one end to provide an annular seal between said piston when said piston is disposed in said first position stop and said piston, means defining an exhaust passage having an orifice disposed for communication with said opposed surface of said piston inside the area of said annular seal, a reservoir chamber for supplying fluid pressure to said cylinder through the open upper end thereof in a piston driving stroke, a first port adjacent said open end of said cylinder, said piston when in said first position engaging said first surface portion blocking communication between said reservoir chamber and said cylinder through said first port, said first port being fully open during the driving stroke of the piston away from said piston stop, and control means maintaining a normal pressure differential across said piston when the latter is disposed in said first position urging said piston into said first position operable to change said normal pressure differential into one resulting in downward movement of said piston away from said piston stop whereby said piston is moved through a driv ing stroke under the action of the pressure in said reservoir chamber, said control means including valve means movable between a first position connecting the lower end of said cylinder to a source of fluid pressure for urging said piston toward said piston stop and a second position connecting the lower end of said cylinder to atmosphere for venting said cylinder.

17. The implement as claimed in claim 16 wherein said valve means includes a valve element and an operating piston coupled thereto, the effective dimension of said operating piston being greater than the corresponding dimension of said valve element.

18. The tool as claimed in claim 16 wherein said valve means includes a flexible diaphragm member.

19. The tool as claimed in claim 16 including a control chamber adjacent said reservoir chamber and a second port communicating said control chamber with said reservoir chamber, and wherein said piston stop includes a 13 second surface portion for sealing said second port said piston stop being mounted for movement between a second port sealing position and a second port opening position, and further including spring means for urging said piston stop towards said second port sealing position.

20. The implement as claimed in claim 19 wherein said piston when urging into engagement with said piston stop moves said second surface portion away from said sealing position into said opening position,

21. The implement as claimed in claim 20 and further including an exhaust valve for controlling the flow of fluid through said exhaust passage and manually operative means for operating said exhaust valve and said control means.

22. Fastener driving apparatus comprising means defining a cylindrical chamber having first and second ends, a simple piston slidably mounted in said chamber for movement between a first position adjacent said first chamber end and a second position adjacent said second chamber end, means defining a drive track for receiving fasteners therein, a fastener driving element operatively connected with said piston for movement in a driving stroke through said drive track to drive a fastener received therein outwardly into a workpiece in response to the movement of said piston from said first position into said second position, means defining a reservoir chamber for containing a supply of fluid under pressure, fluid pressure receiving means separate from said reservoir chamber adapted to be connected with a source of fluid under pressure, actuating means movable from an inoperative position to an operative position under the control of an operator, and fluid pressure control means operable when said piston is disposed in said first position and said actuating means is disposed in said inoperative position (1) to communicate the second end of said cylinder with said fluid pressure receiving means so that source pressure acts on the piston therein to urge the same toward said first position, (2) to communicate said reservoir chamber with said fluid pressure receiving means so that said reservoir chamber is charged with source pressure and (3) to prevent communication of fluid under pressure with the first end of said cylindrical chamber, and operable in response to the movement of said actuating means into said operative position (1) to close communication of said fluid pressure receiving means with said reservoir chamber and the second end of said cylindrical chamber, (2) to exhaust the latter to atmosphere so as to relieve the pressure acting on said piston urging the same toward said first position and (3) to communicate said reservoir chamber with the first end of said cylindrical chamber so that the source pressure contained therein acts on the piston therein to urge the same toward said second position and thereby etfect a rapid driving stroke of said fastener driving element.

23. Apparatus as defined in claim 22 including means defining an exhaust passage closed when said piston is disposed in said first position operable to communicate with said reservoir chamber when said piston is in said second position and said actuating means is in said inoperative position to lower the pressure acting on said piston urging the same into said second position sufficient to effect movement of said piston away from said second position and into said first position in response to the movement of said actuating means from said operative position into said inoperative position.

References Cited UNITED STATES PATENTS 3,063,421 11/1962 Fisher 227-430 X 3,126,630 3/1964 Catlin et al 22710 X 3,162,097 12/1964 Allen et a1.

GRANVILLE Y. CUSTER, JR., Primary Examiner. 

1. A PNEUMATIC DRIVING TOOL COMPRISING A CYLINDER HAVING AN OPEN END, A PISTON DISPOSED IN SAID CYLINDER FOR AXIAL MOVEMENT BETWEEN FIRST AND SECOND POSITIONS INCLUDING A DRIVING STROKE IN A DIRECTION AWAY FROM THE OPEN END OF SAID CYLINDER, A FASTENER DRIVING ELEMENT SECURED TO SAID PISTON AT ONE END THEREOF, A PISTON STOP SPACED ABOVE SAID OPEN END OF SAID CYLINDER INCLUDING A FIRST SURFACE PORTION ENGAGING THE PISTON SURFACE OPPOSED TO SAID ONE END TO PROVIDE AN ANNULAR SEAL BETWEEN SAID PISTON STOP AND SAID PISTON WHEN SAID PISTON IS DISPOSED IN SAID FIRST POSITION, MEANS DEFINING AN EXHAUST PASSAGE HAVING AN ORIFICE DISPOSED FOR COMMUNICATION WITH SAID OPPOSED SURFACE OF SAID PISTON INSIDE THE AREA OF SAID ANNULAR SEAL, A RESERVOIR CHAMBER FOR SUPPLYING FLUID PRESSURE TO SAID CYLINDER THROUGH THE OPEN UPPER END THEREOF IN A PISTON DRIVING STROKE, A FIRST PORT ADJACENT SAID OPEN END OF SAID CYLINDER, SAID PISTON WHEN IN SAID 